Area Forecast Discussion
Issued by NWS Wilmington, NC

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FXUS62 KILM 240800
AFDILM

Area Forecast Discussion
National Weather Service Wilmington NC
300 AM EST Wed Jan 24 2018

.SYNOPSIS...
Seasonably cool, and dry weather will prevail the next several
days, before a warming trend into the weekend. Sunday may see
a few rain-showers, as a cold front crosses the coast. Canadian
high pressure building in early next week, will bring drier and
cooler air to the area.

&&

.NEAR TERM /THROUGH TONIGHT/...
As of 3 AM Wednesday...High pressure to the west will gradually
build over the region through the period. What cold advection
was behind the exiting cold front will be ending this morning
with neutral advection and abundant sunshine resulting in highs
near to slightly above climo. Broad 5h trough will be enhanced
by modest shortwave rounding the base of the longwave trough.
Shortwave passes well north of the area, moving from the KY/OH
Valleys into the Mid- Atlantic today into tonight. The shortwave
will help drag a dry cold front across the region overnight.
Front is moisture starved by deep west-northwest flow and only
clouds with it are likely to be patches of cirrus. Gradient does
tighten up a bit as weak cold advection kicks in. Light to calm
winds in the evening will increase a bit and become northwest
for the end of the period. Mixing will prevent any significant
radiational cooling component however, cold advection overnight
will drop lows into the upper 20s to lower 30s.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 3 AM Wednesday...Exceptionally dry column this period with
precipitable waters, a few ticks either side of a quarter inch.
It is not until late in the period Friday evening, that we see
low-level moisture advection on SE trajectories, in amplifying
return wind-flow, as high pressure slips off the mid-Atlantic
coast. Resurgence of high pressure from the west at the start of
the period, will foster seasonably cool conditions both days,
with the onset of a warming trend Friday afternoon, bringing us
slightly above normal for late January. The breeziest portion
of this period, Thursday morning in N-NNW wind, gusts to 25 mph
at the coast after daybreak. This will bring wind-chills early
on Thursday, deep into the 20s area-wide. On a warmer note,
plenty sunshine minutes appear on tap this period. The only
significant clouds slated, would be Friday night, where batches
of strato-cumulus off the ocean may be arriving.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
As of 3 PM Tuesday...Upper level ridging across the eastern
U.S. Saturday will give way to an approaching upper trough
early next week. There are amplitude differences with the trough
between the GFS and the ECWMF/Canadian/NAVGEM that strongly
influence our sensible weather for Sunday and Sunday night.

Surface high pressure should move off the coast Saturday. This
will allow for a modified marine airmass to spread back onshore
with rising temperatures and dewpoints for Saturday. The
aforementioned upper trough should dig into the eastern U.S.
Sunday and Monday. The GFS is anomalously flatter with this
feature compared to virtually all other models, and the surface
low it develops remains weak and trickles eastward across
Florida. Other models show a stronger surface low moving
northeastward out of the Gulf and through the Piedmont/Foothills
region on Sunday, drawing in a stronger southerly flow across
the coastal Carolinas. Following the more amplified models,
we`re forecasting PoPs increasing to 60-70 percent on Sunday.
Forecast soundings from the ECMWF show modest surface-based
instability possible, and we`ll maintain the mention of isolated
thunderstorms.

All models show clearing developing Monday as a glancing shot of
Canadian air spreads into the Carolinas from the north. Low
temperatures Monday and Tuesday nights could drop to freezing.

&&

.AVIATION /07Z WEDNESDAY THROUGH SUNDAY/...
As of 06Z...High pressure will build in from the west through
the period. The only feature of note will be a dry cold front
crossing the area this evening. Likely see some high clouds with
the front but little more. Front will provide a reinforcing shot
of colder air and kick up northwest winds a bit overnight. VFR
conditions will prevail through the period with generally west
to northwest winds 10 kt or less.

Extended Outlook...VFR through the end of the forecast period.

&&

.MARINE...
NEAR TERM /THROUGH TONIGHT/...
As of 3 AM Wednesday...Flow will remain offshore (west-
northwest) through the period as high pressure builds in from
the west. Gradient will steadily decrease today with northwest
winds dropping under 10 kt by midday. Winds briefly back to
west-southwest this evening before passage of dry cold front
returns winds to west- northwest and increases speeds to 15 to
20 kt after midnight. Offshore flow has helped drop seas under 6
ft this morning thus the SCA expired at 3 AM. Seas will
continue gradually decreasing as winds remain offshore and
weaken through the day. Seas drop as low as 1 to 2 ft late in
the day but the arrival of the next round of cold advection
overnight will build seas back to 2 to 4 ft by the end of the
period.

SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
As of 3 AM Wednesday...N winds a bit frisky at the onset of
this marine period early Thursday, with N wind gusts to 20 kt,
as high pressure barges in from the west. As a result, wind-
seas will build to 4 ft offshore Thursday morning, bumpy yes,
but no advisories or caution headlines are anticipated, although
do know, dominant wave periods will run between 4-5 seconds.
The atmosphere will remain dry this period, so no threat of
TSTMS. Late Friday night in return, and increasing SE wind, a
few showers offshore are possible. On Friday, a lovely marine
day, longer period swell may become the dominant wave energy,
as winds become light during the day, veering to E-SE in the
eve.

LONG TERM /SATURDAY THROUGH SUNDAY/...
As of 3 PM Tuesday...Low pressure should develop in the
northern Gulf of Mexico on Saturday, but where the low moves
Saturday night and Sunday is still quite uncertain. The GFS
model has been very consistent for the last couple of days
showing the low moving eastward across Florida with relatively
little impact on our wind speed or direction locally. The bulk
of the other global weather models show the low moving
northeastward through the Piedmont and Appalachian Foothills
Sunday and Sunday night. The difference we`d see in wind/weather
conditions between these two possibilities is enormous.

Following the consensus solution shown by the ECWMF, Canadian,
and NAVGEM models brings increasing southerly winds across the
Carolina coastal waters Sunday and Sunday night. The long
southerly fetch is expected to bring Small Craft Advisory
conditions due to seas, and probably due to winds too. Showers
will become likely with maybe a few thunderstorms embedded
Sunday night. The cold front associated with the low may reach
the area late Sunday night with winds shifting westerly before
sunrise Monday.

&&

.ILM WATCHES/WARNINGS/ADVISORIES...
SC...None.
NC...None.
MARINE...None.

&&

$$

SYNOPSIS...8
NEAR TERM...III
SHORT TERM...Colby
LONG TERM...TRA
AVIATION...III



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